Patients who have a lumbar spinal fusion have an increased risk of having adjacent segment disease. Adjacent segment disease occurs after the spinal fusion in which the segment or the intervertebral disc and the facet joints are degenerated at the adjacent level above or below the lumbar fusion.
Often, a disorder in one spinal component can lead to ultimate disorder in an adjacent component of the spine. In such cases, both components will ultimately require a spinal fusion. However, if the adjacent spinal component (that is partially diseased) is fused with the fully diseased component, the patient will not only lose more mobility in the spine, but the partially diseased component will degrade quicker. Thus it may be desired to not fully immobilize the adjacent spinal component that is only partially diseased.